Intraocular lenses (IOLs) are implanted in patients' eyes either to replace a patient's lens or to complement the patient's lens. The IOL may be implanted in place of the patient's lens during cataract surgery. Alternatively, an IOL may be implanted in a patient's eye to augment the optical power of the patient's own lens.
Some conventional IOLs are single focal length IOLs, while others are multifocal IOLs. Single focal length IOLs have a single focal length or single power. Objects at the focal length from the eye/IOL are in focus, while objects nearer or further away may be out of focus. Although objects are in perfect focus only at the focal length, objects within the depth of field (within a particular distance of the focal length) are still acceptably in focus for the patient to consider the objects in focus. Multifocal IOLs, on the other hand, have at least two focal lengths. For example, a bifocal IOL has two focal lengths for improving focus in two ranges: a far focus corresponding to a larger focal length and a near focus corresponding to a smaller focal length. Thus, a patient's distance vision and near vision may be improved. A conventional diffractive bifocal IOL typically uses the 0th diffractive order for distance focus/vision and the 1st diffraction order for near focus/vision. Trifocal IOLs have three foci: a far focus for distance vision, a near focus for near vision and an intermediate focus for intermediate vision that has an intermediate focal length between that of the near and far focuses. A conventional diffractive trifocal IOL typically uses the 0th diffractive order for distance vision, the 1st diffractive order for intermediate vision and the 2nd diffraction order for near vision. Multifocal IOLs may improve the patient's ability to focus on distant and nearby objects. Stated differently, the depth of focus for the patient may be enhanced.
Although multifocal lenses may be used to address conditions such as presbyopia, there are drawbacks. Multifocal IOLs may also suffer from longitudinal chromatic aberration. Different colors of light have different wavelengths and, therefore, different foci. As a result, the multifocal IOL focuses light of different colors at different distances from the lens. The multifocal IOL may be unable to focus light of different colors at the patient's retina. The polychromatic image contrast for the multifocal IOL, particularly for distance vision, may be adversely affected.
Accordingly, what is needed is a system and method for addressing chromatic aberration in multifocal IOLs.